Jason Kidd has an unlikely ally in his feud with Mark Cuban — his arch-nemesis ex-wife Joumana… who tells TMZ the former Mavs superstar DESERVES to have his jersey retired in Dallas

Joumana tells TMZ … that just ain’t the case … and despite her rocky relationship with Jason, she believes the 39-year-old — who played a key role on the Mavs 2011 championship team — should be treated like the hoops hero he is.

“[Jason] is an amazing basketball player I can never take that away from him. He’s one of the best guards to ever play in the league. “

She adds, “Lots of fans would love to see his jersey retired in Dallas … I believe he’s earned it and he deserves that based on what he did for the Mavericks.”